Scientists have proved for the first time that fructose, a cheap form of sugar used in thousands of food products and soft drinks, can damage human metabolism and is fueling the rise in obesity. Previous research has focused of the potentially adverse impact of fructose on rats, but this first experiment involving humans has now revealed serious health concerns.

Although this sweetener is found naturally in small quantities in fruit, it is increasingly been used as a substitute for more expensive types of sugar in yoghurts, cakes, salad dressing, cereals and even some fruit drinks.

Over 10 weeks, 16 volunteers on a controlled diet including high levels of fructose produced new fat cells around their heart, liver and other digestive organs. They also showed signs of food-processing abnormalities linked to diabetes and heart disease. Another group of volunteers on the same diet, but with glucosesugar replacing fructose, did not have these problems.

Fructose bypasses the digestive process that breaks down other forms of sugar. It arrives intact in the liver where it causes a variety of abnormal reactions, including the disruption of mechanisms that instruct the body whether to burn or store fat.

Natural fructose represents 5%-10% of the weight of any fruit. A synthesized version which uses a combination of fructose and glucose syrup from maize is increasingly being used in processed foods as a cheaper ingredient and six times sweeter than cane sugar. It is called high-fructose corn syrup, or glucose-fructose syrup, and to make matters worse, all of the fiber has been removed from these processed foods, so there is essentially no nutritive value at all.

Firstly, the body metabolizes fructose in a much different way than glucose. The entire burden of metabolizing fructose falls on the liver. In simple terms, when too much fructose enters the liver, the liver can't process it all fast enough for the body to use as sugar. Instead, it starts making fats from the fructose and sending them off into the bloodstream as triglycerides. Triglycerides are potential risk factors for obesity, heart disease and type-2 diabetes.

Secondly, fructose is being consumed in enormous quantities, which has made the negative effects much more profound. All fructose works the same in the body, whether it comes from corn syrup, cane sugar, beetsugar, strawberries, onions, or tomatoes. Only the amounts are different.

The bottom line is that fructose leads to increased weight gain, insulin resistance and metabolic syndrome - not to mention the long list of chronic diseases that directly result. So try to avoid fructose and other artificial sweeteners as much as possible.